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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS011 Poster presentation 2168
Deformation experiments on Marble under true triaxial stress states
Mr. Shotaro Nakayama
Earthquake Prediction Research Center Earthquake Research Institute
Hiromine Mochizuki, Masao Nakatani, Shingo Yoshida
Although effect of the intermediate principal stress virtually has been done, to our knowledge, it has
been only known for a brittle regime (e.g. Mogi, 1971). However, because of the stress states in the
deep crust with directional tectonic force, it is obviously important to clarify the deformational behavior
of rocks during plastic flow under true triaxial stress states, in which the intermediate principal stress is
not equal to the minimum or maximum principal stress. We performed deformation experiments by
applying three principal stresses independently: sigma1 by vertical pistons, sigma2 by horizontal pistons
and sigma3 by confining pressure. All tests, true and conventional triaxial compression tests, at constant
piston displacement rates were conducted using marble at dry and wet conditions. Temperature was
300 C and effective confining pressure was 220 MPa for the all experiments. True triaxial compression
tests at high temperature and pressure were successfully performed, and two stress-starin curves,
sigma1- sigma3 vs. epsilon1 and sigma2- sigma3 vs. epsilon2, were obtained. From experiments carried
out at different strain rates, it was found that flow stress, sigma1- sigma3, significantly increased with
sigma2. Description of a flow property under true triaxial stress state using the Von Mises equivalent
flow stress and strain rate, which was suggested by Paterson (1987), has been tried. A sample
deformed under a true triaxial stress state was cut in three planes, each of which was perpendicular to
each principal stress. All of them showed clear evidence of microstructures which was not seen in an
undeformed sample. In addition, there were slight differences in microstructures of the 3 planes which
were presumably caused by a true triaxial stress state.
Keywords: true triaxial, flow, marble